SAP PO integration with Sharepoint 2013

All-

More of an architectural Question.

Background: We have fresh installation of SAP PO 7.3 (Single Stack ) on SQL Server 2013.

Moving forward we will be
creating all Forms(FI manual Invoice, 11 forms) on SharePoint 2013. The SharePoint team is also responsible for Worksflow triggered with it. Once the workflow is routed and approved on SharePoint- then this information of Form needs to be posted to SAP…

This is where SAP PO will be used, now we have 3 options identified for this- Please let me know the best solution

1. We will  create SharePoint items with the basic Form .
2. SharePoint will route the approval of Workflow. We do not need to worry
3. Determine the Interface between  the SharePoint and SAP
   1. SharePoint make SOAP request to SAP Webservice. SAP PO will be providing with URL/Web service/WSDL  Endpoint and login credentials details to the Sharepoint team.
   2. SharePoint puts record in SQL Server Database and PO will write a SQL query for pulling the data(JDBC)
   3. Duet Connection- We are currently not planning to use this approach if it is feasible by SAP PO.
4. After the connection is established between SharePoint and SAP, we will post the data into SAP using RFC ?!?
5. From SAP we will give the Response back to the SharePoint sayings Success/Failure ?!?

Please help me with pro's and con's of point 3,and let me know the feasibility of 4 and 5.

I always reward points for any answers-

Thanks in advance.